Method and apparatus for removing grease from within an exhaust system

ABSTRACT

A method and apparatus for removing grease buildup from within an exhaust system of the type utilized in restaurants to vent vapors from a cooking facility. The exhaust duct system typically includes a canopy positioned above a cooking facility to collect grease laden vapors from a cooking unit and an exhaust duct connected to the canopy to vent the collected vapors to the atmosphere. The improvement of the subject invention includes a liner removably attached to the interior surface of the canopy to provide a surface for the collection of grease and thereby isolate the canopy from the collection and buildup of grease and a liner removably attached to the interior surface of the exhaust duct to provide a surface for the collection of grease and thus isolate the exhaust duct from the collection and buildup of grease. The method includes the steps of lining the canopy and exhaust duct with removable and replaceable liners and upon the detection of a substantial buildup of grease within the exhaust system removing the liners and inserting cleaned or new liners within the exhaust system.

United States Patent [191 Van Schoyck METHOD AND APPARATUS FOR REMOVINGGREASE FROM WITHIN AN EXHAUST SYSTEM [75] Inventor: Quentin H. VanSchoyck, Christmas,

Fla.

[73] Assignee: Cylpik, Incorporated, Winter Park,

Fla.

[22] Filed: Aug. 23, 1973 21 Appl. No.: 390,756

[52] US. Cl. 126/299 A; 126/299 C; 98/115 K {51] Int. Cl. F24c 15/20[58] Field of Search 98/115 K, 115 R; 126/299 R, 299 A, 299 B, 299 L,120, 121;

55/DIG. 36, 435; 432/252; 52/218, 219

['56] References Cited UNITED STATES PATENTS 949,620 2/1910 Chastant126/299 A 1,192,078 7/1916 Laberge... 126/299 A 1,457,540 6/1923Matthews 126/120 1,855,050 4/1932 Hentschel.... 126/299 A 2,746,4485/1956 Holmsten 126/299 C 2,806,227 9/1957 Arbetter... 126/299 C2,841,132 l/l958 Philipp 126/299 C 2,886,124 5/1959 Scharmer 126/3012,887,154 5/1959 Morningstar et al 126/299 C 3,190,281 6/1965 Northwood126/120 FOREIGN PATENTS OR APPLICATIONS 363,143 12/1931 United Kingdom126/299 C Oct. 14, 1975 Primary ExaminerCharles .1. Myhre AssistantExaminer-Pau1 Devinsky Attorney, Agent, or Firm-Bums, Doane, Swecker &Mathis ABSIRACT A method and apparatus for removing grease buildup fromwithin an exhaust system of the type utilized in restaurants to ventvapors from a cooking facility. The exhaust duct system typicallyincludes a canopy positioned above a cooking facility to collect greaseladen vapors from a cooking unit and an exhaust duct connected to thecanopy to vent the collected vapors to the atmosphere. The improvementof the subject invention includes a liner removably attached to theinterior surface of the canopy to provide a surface for the collectionof grease and thereby isolate the canopy from the collection and buildupof grease and a liner removably attached to the interior surface of theexhaust duct to provide a surface for the collection of grease and thusisolate the exhaust duct from the collection and buildup of grease. Themethod includes the steps of lining the canopy and exhaust duct withremovable and replaceable liners and upon the detection of a substantialbuildup of grease within the exhaust system removing the liners andinserting cleaned or new liners within the exhaust system.

9 Claims, 19 Drawing Figures U.S. Patent Oct.14,l975 Sheet1of3 3,911,895

US. Patent Oct. 14, 1975 Shaet 2 of3 3,911,895

US. Patent Oct. 14,1975 Sheet3of3 3,911,895

METHOD AND APPARATUS FOR REMOVING GREASE FROM WITHIN AN EXHAUST SYSTEMBACKGROUND OF THE INVENTION This invention pertains to a method andapparatus for removing grease buildup from within an exhaust system ofthe type utilized to vent vapors from a restaurant cooking facility.

In the restaurant industry typical cooking facilities which are utilizedinclude ovens, grills, french fryers, etc. These devices all generate aconsiderable amount of grease laden vapors during a cooking operation.The vapors are collected within a hood or canopy overlying the cookingunit and are vented to the atmosphere through an exhaust duct system.

The grease laden vapors tend to cool during passage through the exhaustsystem and condense upon the interior surfaces of the canopy and exhaustducts. Over a period of time and intermittent use grease depositsaccumulate until the interior of the entire exhaust system is coatedwith a glaze of grease.

This grease buildup is highly flammable and presents a significant andcontinuously vexing fire hazard to the restaurant industry.

Although a real and continuing danger exists with respect to the buildupof grease within exhaust systems, restaurant owners frequently tend tobe dilatory in connection with maintenance of such exhaust systems, fora number of reasons.

In this connection it is infeasible, as a practical matter, toadequately determine or measure the amount of grease'buildup within anexhaust system which is typically enclosed and inaccessible for readyinspection. Therefore, it is difficult to determine if cleaning ormaintenance is really necessary. A further condition which significantlydetracts from enthusiasm for maintaining the exhaust system in a firesafe condition comprises excessive difficulty, in terms of time andlabor, in cleaning the exhaust system. This difficulty is accentuated inmulti-story buildings where an exhaust system may run vertically throughseveral floors.

In the past two techniques have been primarily utilized to maintain anexhaust system in at least a theoretically grease free condition. Thesetwo systems included (l) steam cleaning; and (2) scraping of the exhaustsurfaces with subsequent application of calcium hydroxide or calciumchloride.

Notwithstanding extensive utilization of these two systems in the past,substantial difficulties have been occasioned in attempting to utilizeeither of these previously known cleaning techniques.

More specifically and in connection with the previously known steamcleaning technique, the exhaust system tends to be inundated with watercondensed during the cleaning operation. Further, and in this same vein,steam equipment is often difficult to control, thus providing anoverspray of water onto other facilities and equipment. Moreover,complete removal of buildup resins and carbon is extremely difficult toobtain with steam cleaning equipment. Still further the work isextremely laborious. Consequently it is difficult to obtain laborers towork with such equipment.

With respect to the utilization of calcium hydroxide or calciumchloride, cleaning, scraping and coating techniques, it is extremelydifficult to initially remove all of the collected grease from theexhaust ducts. Consequently in many cases only the surface layer ofcarbon and grease is removed. When calcium hydroxide or calcium chlorideis mopped onto a surface already containing a buildup of carbon andgrease, the problem is merely accentuated. In this connection thesecompounds tend to combine with the grease and carbon on the duct wallsto build up a resin like substance which is extremely flammable onceignited. Further, these calcium compositions tend to continuously flakeinto the duct system potentially dropping cleaning materials onto thecooking unit or in low areas of the exhaust system. Still further, whilethe labor needed to utilize this technique is not as great as in steamcleaning, the quality or degree of fire protection obtained is onlymarginal.

Accordingly, notwithstanding the fact that grease laden exhaust systemshave been at least theoretically cleaned in the past substantial roomfor improvement remains.

It would therefore be desirable to provide a method and apparatus whichwould minimize the difficulty and hazard of cleaning exhaust systemswhile increasing the reliability and quality of the completed work.Further it would be desirable to minimize the time and labor expenseinvolved in an exhaust system cleaning operation. Still further it wouldbe highly advantageous to provide a cleaning system operable inconnection with multi-story high rise buildings, where accessibilitywithin tall vertical ducts presents a significant problem.

OBJECTS OF THE INVENTION It is therefore a general object of theinvention to provide a novel method and apparatus for removing greasebuildup upon the interior surface of an exhaust system in a manner whichwill obviate or minimize problems of the type previously described.

It is a particular object of the invention to provide a novel method andapparatus for cleaning an exhaust system wherein the reliability andquality of the cleaning operation is maximized.

It is a further object of the invention to provide a novel method andapparatus for cleaning an exhaust system wherein the time required forthe cleaning operation is minimized.

It is yet a further object of the invention to provide a novel methodand apparatus for cleaning an exhaust system which will minimize thelaborous character of the operation of heretofore attendant exhaust ductcleaning operations.

It is another object of the invention to provide a novel method andapparatus for cleaning an exhaust system which is operable toeffectively clean the interior of long vertical spans of exhaust ductsin high rise buildings and the like.

It is still another object of the invention to provide a novel methodand apparatus for cleaning an exhaust system which insures completecarbon and grease removal from the exhaust system.

It is yet another object of the invention to provide a novel method andapparatus for lining an exhaust system with a readily removable andreplaceable liner upon detection of a buildup of grease within theexhaust system.

BRIEF SUMMARY OF THE INVENTION A method and apparatus for achieving atleast some of the foregoing objects includes a liner removably attachedto the interior surface of a canopy to provide a surface for thecollection of grease and thereby isolate the canopy from the collectionand buildup of grease and a liner removably attached to the interiorsurface of an exhaust duct to provide a surface for the collection andbuildup of grease and thus isolate the exhaust duct from a substantialbuildup and collection of grease. The method includes the steps oflining the canopy and exhaust ducts with removable, replaceable linersand upon the detection of a substantial buildup of grease with theexhaust system removing the liners and inserting cleaned or new linerswithin the exhaust systern.

THE DRAWINGS Further objects and advantages of the invention will becomeapparent from the following detailed description taken in conjunctionwith the accompanying drawings wherein:

FIG. 1 is an axonometric view of an exhaust system of the type utilizedin a typical restaurant kitchen to vent grease laden vapors from acooking unit;

FIG. 2 is a fragmentary perspective view of a canopy portion of anexhaust system taken from the inside thereof looking upwardly and towardthe front;

7 FIG. 3 is a transverse sectional view through a typical canopy withliner panels according to the subject invention shown in schematic andexploded perspective;

FIG. 4 is an axonometric view of a typical canopy liner panel accordingto the subject invention;

FIG. 5 is a fragmentary axonometric view with parts broken awaydisclosing a portion of the duct system directly above an exhaust canopyincluding a duct liner assembly according to the subject invention;

FIG. 6 is a broken away detailed view of a section of the liner of thesubject invention;

FIG. 7 discloses one technique of securing a liner according to thesubject invention to a clamping bar for attachment to a duct wall;

FIG. 8 discloses an alternative means of securing a liner systemaccording to the subject invention to a clamping bar for securing theliner to a duct wall;

FIG. 9 discloses still another means of securing a liner according tothe subject invention to the side wall of a duct unit;

FIG. 10 is a typical cross sectional view through the fastener assemblyas disclosed in FIG. 9;

FIG. 11 is a typical schematic cross section through a generallyhorizontal portion of the duct assembly upstream from the exhaustcanopy;

FIG. 12 is a typical schematic cross section through a first generallyvertical duct segment extending between a canopy and a horizontal ductsegment as depicted in FIG. 5;

FIG. 13 is a detailed view of an assembly for raising and lowering aliner panel within the interior of an exhaust conduit according to thesubject invention;

FIG. 14 is a side elevational view of the raising and lowering assemblydepicted in FIG. 13;

FIG. 15 is a typical cross sectional detailed view taken along section1515 in FIG. 13;

FIG. 16 is a plan view of the raising and lowering mechanism accordingto FIGS. 13 and 14;

FIG. 17 is a typical cross sectional view through a vertical duct with aremovable liner attached thereto according to the subject invention;

FIG. 18 is a typical cross sectional detailed corner view as circled inFIG. 17; and

FIG. 19 is a detailed view of an assembly for maintaining tension upon aduct liner according to the subject invention at a base portion of theduct.

DETAILED DESCRIPTION Context of the Invention Before discussing indetail an illustrative embodiment of the subject invention it may behelpful to identify the context of the invention in terms of anenvironment of primary utilization. In this connection, and withreference to FIG. 1, there will be seen an exhaust system 20 of the typeutilized in a restaurant kitchen 22, including a canopy 24 positionedgenerally vertical above a cooking facility 26. The cooking facility 26may include a grill portion 28, an oven 30 and a french fryer unit 32,etc. Each of these cooking devices tend to generate grease vapors duringcooking operation which vapors rise by convection and are collectedwithin the overlying canopy 24.

The exhaust system 20 further includes a main vertical duct 34 whichextends through multiple floors 36 of the restaurant building and exitsat the upper end 38 thereof into the atmosphere. The main vertical duct34 may extend directly into the canopy 24 or may be connected thereto byan L-shaped duct 40.

As previously discussed, the grease vapor is collected within the canopy24 and vented to the atmosphere through the ducts 34 and 40. As the hotvapors pass into the canopy and through the duct system, they tend tocool and deposit grease upon the interior surface of the canopy and theexhaust duct system. This grease over a period of time tends to build upwithin the exhaust system and presents a significant fire hazard.

The subject invention is directed to a method and apparatus formaintaining an exhaust system, typically of the foregoing type, in arelatively clean, grease-free condition by the provision of a removableliner assembly which obviates or minimizes problems of the typepreviously described.

Exhaust System Canopy Referring specifically now to FIGS. 24, there willbe seen a typical canopy assembly 24 of the type previously discussedoperable to collect vapors and to funnel the collected vapors into anexhaust duct 40. In order to minimize the amount of grease that passesinto the duct system, a conventional tortuous path filter 42 isfrequently positioned across a back wall 44 of the canopy.

The canopy 24 includes a generally horizontal top wall 46 and a slopingfront wall 48. The canopy is enclosed with sloping end walls 50 and 52.

According to the subject invention each of these walls are covered by aremovable liner system 52 such as illustrated in FIG. 2. This linersystem includes a plurality of individual panels 54 which are attachedto the inner surface of the canopy along the side wall by metallicstrips 58 and sheet metal screws 60. The corners are fastened by angleiron strips 62 and sheet metal screws 63. At the bottom edge of thecanopy, which is normally fashioned with a grease trough 64, note FIG.3, the panels 54 are appropriately contoured and connected to anupwardly projecting lip 66 by the provision of metallic clips 68.

Each of the panels 54, as illustrated in FIG. 5 is a relatively smallmember as compared with the overall extent of the canopy and thus iseasily removable and can be handled by a single laborer. Accordingly,once the panels 54 are removed, each panel may be individuallytransported and cleaned within a vat in a convenient and accessibleposture.

When it is anticipated that removal and cleaning will be desired, thepanels 54 are typically composed of a galvanized sheet material or astainless steel which will resist corrosion. Alternative the individualpanels 54, note FIG, 4, may be fashioned from thin aluminum sheetmaterial which upon removal may be discarded and a new sheeting may bereadily fashioned and applied.

It should be appreciated that removal and cleaning or removal anddiscarding is a substantial advance in terms of cleaning of a canopywhen considered with respect to the difficulty a worker might encounterwith respect to scraping grease or utilizing steam spraying equipmentprojected upwardly within the interior of the canopy.

Duct Liner System Referring now particularly to FIGS. 5 and 6 there willbe seen a liner assembly or lamina 80 of the type utilized to line anexhaust duct according to the subject invention. More particularly theexhaust system liner is fabricated with a metallic backing member 82which may be, for example, a wire mesh or screen composed of galvanizedcopper, aluminum or steel. The wire backing member 82 provides form andstrength to the liner assembly. The liner is further composed of aninnermost sheet 84 of asbestos material. Asbestos is preferred becauseof its resistance to burning and porosity or ability to collect and holdgrease that tends to deposit upon the duct wall.

In one preferred embodiment a vapor barrier 86 is interclad between theasbestos inner liner 84 and the metallic backup member 82. This liner ispreferably fabricated from a fireproof paper, such as NOMEX paper. NOMEXis a trademmark of the E. I. duPont de Nemours & Co. and comprises aheat-resistant nylon, the copolymer of meta-phenylenediamine andisophthaloyl chloride. It retains useful properties after longtermexposure to temperatures up to 220C. and does not support combustion.

The lining composition 80 is applied throughout the interior of theexhaust system.

The liner is applied within small vertical section 88 of duct 40 and isheld at the corners by the provision of angle iron strips 90. Thesestrips 90 are removably attached at the corners of the duct walls bysheet metal screws, not shown. The bottommost portion 92 of the liner isconnected to the wall by fastening means such as detailed in FIGS. 7 and8.

More specifically in FIG. 7 there is disclosed a metal cleat or clip 94which is resilient and is designed to interferingly fit about a lowerportion of the liner 80 which is wrapped around a horizontal edge bar 96of the vertical duct wall 88.

An alternative attachment assembly is disclosed in FIG. 8 and in thisconnection a horizontal metallic strip 98 is depicted as being rivetedto the liner composition 80 by rivets 100. The metallic strip 98 maythen be secured to the duct wall 88 by the provision of a sheet metalscrew 102, note particularly FIGS. 5 and 8.

Access to the vertical duct segment 88 is provided by a removable panel92 to facilitate inspection and application, removal and replacement ofthe short liner segment.

In some instances it is desired to pin mid span portions of the lineragainst the duct walls. This may be accomplished by the provision of pinlock assemblies 104, such as detailed in FIGS. 9 and 10. Morespecifically a metallic base 106 is spot welded to a portion of a ductwall 108. The base is provided in a central portion thereof with anormally extending post 110. The post is fashioned with a sharp point112 which is operable to penetrate the liner composition 80. The linermay be pinned upon the post by the application of a circular mountingpad 114, having a small central aperture 116 designed to interferinglyfit with the post 110, note particularly FIG. 10.

Referring now specifically to FIGS. 11 and 12, there is disclosedtypical schematic cross sectional views taken through the horizontalduct portion 120 and the vertical duct portion 88 of the L-shapedconnecting section 40. In this connection in the horizontal duct portion120 the liner 80 may be a continuous wrapping which is overlapped at.its edge as at 122 and is removably connected to the duct 120 by theprovision of corner strips 124 which may be attached to the interiorsurface of the duct 120 by the provision of sheet metal screws, notshown.

Referring now to FIG. 12 there is disclosed a typical schematic crosssection of the vertical duct portion 88 and illustrating analternativemanner of lining the duct wherein four panels 126, 128, and 132 areutilized. The edges of panels 128 and 132 underly the edges of panels126 and 130 and thus when these members are affixed to the duct cornersby angle strips 90, note F IG. 5, an overlapping sea] at the edges willbe provided.

With particular reference now to FIGS. l3-19 there will be seen a systemfor lining a vertical duct portion of the exhaust system which may beadvantageously utilized to line even long spans such as exist inmultistory buildings. More particularly the liner 80 is wrapped aroundwire cables 134 and 136 at the edges thereof, note particularly FIG. 15,and securely attached thereto by conventional fasteners 138. The panels80 typically are preformed and wound upon large rolls for positioning atthe base of the vertically extending duct portion 34. Housing cables 140and 142, corresponding to cables 134 and 136 may then be lowered fromthe uppermost portion 144 of the duct 134 and attached to the linercable by cleats 146 and 148, respectively.

The hoisting cables 140 and 142 pass over sheathes 150 and 152 and arewound upon a dual winch system including spools 154 and 156,respectively. These spools are simultaneously wound by a common axle 158which may be controlled by a hand lever 160. The take up spools 154 and156 are mounted upon suitable brackets 162 and 164 which in turn areremovably connected to support plates 166 and 168 by conventionalthreaded fasteners 170 and 172.

The take up winch assembly is rendered horizontally adjustable by thrprovision of brackets 162 and 164 which are adjustably connected upon ahorzontally extending bar 174. Thus, as illustrated more clearly in FIG.16, the hand operated take up winch assembly 150 may be moved around thesides of the duct 34 and sequently positioned for support uponpermanently mounted support plates 166, 168, 176 and 178.

Once one panel or liner 80 is raised to cover one side wall of thevertical duct 34, the panel may be attached at the uppermost portionthereof onto the upper edge 144 of the duct 34 by mechanical fasteningmeans extending through the duct and a horizontally extending supportbar 180 positioned across the liner.

In a preferred embodiment, note FIG. 17, a first panel 182 is raised andsecured within the duct 34. A second oppositely positioned panel 184 isthen raised and positioned within the duct. Sequentially then end panels186 and 188 are raised and secured within the duct.

With reference now particularly to FIG. 18, which is a blown upsectional view of a corner of the subject duct assembly, it will be seenthat panel 186 at an edge portion 190 is designed to overlay panel 184.The cables within the edges of the panels 184 and 186 are stretchedtautly to draw the liner into the corners of the duct 34 to hold theliners against the interior surface of the vertical duct.

Maintenance of the liner against the duct walls may be furtherfacilitated by the application of a plurality of clamping assembliessuch as illustrated and previously described in connection with FIGS. 9and 10.

Additionally spring loaded telescoping cross braces 187 and 189 (noteFIG. 17) may be inserted at a plurality of elevations within the duct 34at access locations 191 (note FIG. 1).

Still further, the liners 80 may be additionally induced to lie againstthe duct wall 34 by the application of continuous downward tension uponthe liner by a biasing device 200, note particularly FIG. 19. Morespecifically the liner 80 is provided at its lower end by a horizontallyextending metal bar 202 which is provided with a spring bias assembly204 to bias the lowermost portion of the liner 80 against the duct wall34.

A downward bias is applied to the biasing assembly 204 by the provisionof a second biasing assembly 206 which is normally connected to assembly204. In order to permit movement of assembly 204 in a verticaldirection, a slot 208 is fashioned within the duct wall 34. Thus spring210 of assembly 206 serves to bias the liner 80 in a downward directionand facilitate the maintenance of the liner against the duct wall 34.

Once the liner has been installed within the L-section 40 and thevertical section 34 of the exhaust duct system, the cooking facility 26is utilized in a conventional manner. The liner is periodicallyinspected to determine the quantity of grease buildup upon the linerwall. Once it has been determined that a sufficient grease buildup hasoccurred so as to require removal, the liner is merely removed byreversing the foregoing process. At this point in time the asbestoslayer may be stripped from its metal backing sheath and a new cleanlayer applied. The reassembled liner free of grease accumulation is thenpulled back into the exhaust system.

Alternatively the entire liner may be discarded and an entirely newliner including metal backing member may be inserted.

SUMMARY OF THE MAJOR ADVANTAGES OF THE INVENTION In discussing apreferred embodiment of the invention, several distinct advantages ofthe invention have been specifically and inherently delineated.

More particularly a principle advantage of the subject novel method andapparatus comprises the provision of the removable liner positionedwithin a canopy of an exhaust system in combination with a removableliner positioned within the duct system. These liners may be removed andreplaced or removed and cleaned and thus eliminate difficultiespreviously associated with in situ steam and chemical cleaningoperations.

By the provision of the subject invention, the completeness and qualityof the cleaning operation is substantially enhanced while significantlyreducing the difficulty and the amount of time required to clean a ductsystem. Further local authorities charged with minimizing potential firehazard in a community are provided with a positive means by regulatingthe frequency of which the liners must be replaced.

A further significant advantage pertains to the ease of application andbroadening the base of work force willing to encounter the task ofcleaning exhaust systems.

Still further the subject invention provides a ready means for liningand replacing linings in exhaust ducts even when great heights areencountered.

Other significant advantages pertains to the novel method and apparatusfor mounting the liners within and against the exhaust duct walls.

While the invention has been described with reference to preferredembodiments, it will be appreciated by those skilled in the art thatadditions, deletions, modifications and substitutions or other changesnot specifically described may be made which will fall within thepurview of the appended claims.

What is claimed is:

1. An exhaust duct system of the type utilized to vent grease ladenvapors from a cooking facility including a canopy positioned above thecooking facility to collect grease laden vapors from the cookingfacility and an exhaust duct connected to the canopy to vent thecollected vapors to the atmosphere wherein the improvement comprises:

a liner removably attached to the interior surface of said canopy toprovide a surface for the collection of grease and thereby isolate thecanopy from the collection and buildup of grease; and

a liner removably attached to the interior surface of said exhaust ductto provide a surface for the collection of grease and thereby isolatethe exhaust duct from the collection and buildup of grease, said exhaustduct liner comprising:

a flexible lamina including a metallic base member connected to andoperably supporting an overlay of asbestos sheet material, said linerbing fashioned into four rectangular strips with each strip operable tooverlie one side of a rectangular duct, each of said liner strips havingembedded in the long edges thereof a flexible cable and extending withinsaid exhaust duct in the corners thereof to conform the rectangularliner strips to the interior surface of the exhaust duct.

2. An exhaust duct system of the type utilized to vent grease ladenvapors from a cooking facility as defined in claim 1 and furthercomprising a plurality of pin locking assemblies pinning the liner tothe interior surface of the exhaust duct, said pin locking assemblieseach comprising,

a base member fixedly attached to the interior surface of the exhaustduct,

a post normally projecting inwardly within the exhaust duct from saidbase member and being operable to pass through the liner, and

a locking pad having a central aperture operable to receive said post ininterferring contact and to thereby retain the liner snuggly against theexhaust duct wall.

3. An exhaust duct system of the type utilized to vent grease ladenvapors from a cooking facility including an exhaust duct wherein theimprovement comprises:

a liner removably attached to the interior surface of said exhaust ductto provide a surface for the collection of grease and thereby isolatethe exhaust duct from the collection and buildup of grease, said linercomprising a flexible lamina including a metallic base member connectedto and operably supporting an overlay of asbestos material, said linerbeing fashioned into four rectangular strips with each strip operable tooverlie one side of a rectangular duct, each of said liner strips havingembedded in the long edges thereof a flexible cable and extending withinsaid exhaust duct in the corners thereof to conform the rectangularliner strips to the interior surface of the exhaust duct.

4. An exhaust duct system of the type utilized to vent grease ladenvapors from a cooking facility as defined in claim 3 and furthercomprising a plurality of pin locking assemblies pinning the liner tothe interior surface of the exhaust duct, said pin locking assemblieseach comprising,

a base member fixedly attached to the interior surface of the exhaustduct,

a post normally projecting inwardly within the exhaust duct from saidbase member and being perable to pass through the liner, and

a locking pad having a central aperture operable to receive said post ininterferring contact and to thereby retain the liner snuggly against theexhaust duct wall.

5. A method for lining an exhaust duct 0f the type typically utilized tovent grease laden vapors from a cooking facility comprising the stepsof:

a. providing a rectangular flexible sheet of lining material;

b. attaching flexible cables to the long edges of said lining material;

c. attaching a dual spool winch at the top of the exhaust duct;

d. lowering a flexible cable from each winch spool down through theexhaust conduit;

e. attaching the free ends of the lowered flexible cables to the freeends of the cables attached to the lining material;

f. turning the cables up on the dual spool winch to raise the linermaterial into the interior of the exhaust conduit;

g. securing the lining material within the interior of the exhaust duct;and repeating steps (a)( g) until the entire exhaust duct is lined withstrips of lining material.

6. A method for maintaining an exhaust system in a condition free fromobjectionable buildup of grease deposits as defined in claim 5 whereinsaid step of lining the interior surface of the exhaust duct comprises:

combining into a flexible lamina a metallic base member and a layer ofasbestos sheet material, and

attaching the flexible lamina within and throughout the extent of theexhaust duct.

7. A method for maintaining an exhaust system in a condition free fromobjectionable buildup of grease deposits as defined in claim 6 whereinsaid step of combining further includes the step of:

positioning a vapor barrier between said metallic base member and saidsheet of asbestos prior to attaching the flexible lamina within theinterior of the exhaust duct.

8. A method for lining an exhaust duct of the type typically utilized tovent grease laden vapors from a cooking facility as defined in claim 5wherein said step of providing a flexible liner comprises the step of:

laminating a rectangular strip of metallic base member and a coextensiverectangular strip of asbestos sheet material.

9. A method for lining an exhaust duct of the type typically utilized tovent grease laden vapors from a cooking facility as defined in claim 8wherein said step of laminating further includes:

positioning a rectangular vapor barrier strip between the metallic basemember and the asbestos sheet material.

1. An exhaust duct system of the type utilized to vent grease ladenvapors from a cooking facility including a canopy positioned above thecooking facility to collect grease laden vapors from the cookingfacility and an exhaust duct connected to the canopy to vent thecollected vapors to the atmosphere wherein the improvement comprises: aliner removably attached to the interior surface of said canopy toprovide a surface for the collection of grease and thereby isolate thecanopy from the collection and buildup of grease; and a liner removablyattached to the interior surface of said exhaust duct to provide asurface for the collection of grease and thereby isolate the exhaustduct from the collection and buildup of grease, said exhaust duct linercomprising: a flexible lamina including a metallic base member connectedto and operably supporting an overlay of asbestos sheet material, saidliner bing fashioned into four rectangular strips with each stripoperable to overlie one side of a rectangular duct, each of said linerstrips having embedded in the long edges thereof a flexible cable andextending within said exhaust duct in the corners thereof to conform therectangular liner strips to the interior surface of the exhaust duct. 2.An exhaust duct system of the type utilized to vent grease laden vaporsfrom a cooking facility as defined in claim 1 and further comprising aplurality of pin locking assemblies pinninG the liner to the interiorsurface of the exhaust duct, said pin locking assemblies eachcomprising, a base member fixedly attached to the interior surface ofthe exhaust duct, a post normally projecting inwardly within the exhaustduct from said base member and being operable to pass through the liner,and a locking pad having a central aperture operable to receive saidpost in interferring contact and to thereby retain the liner snugglyagainst the exhaust duct wall.
 3. An exhaust duct system of the typeutilized to vent grease laden vapors from a cooking facility includingan exhaust duct wherein the improvement comprises: a liner removablyattached to the interior surface of said exhaust duct to provide asurface for the collection of grease and thereby isolate the exhaustduct from the collection and buildup of grease, said liner comprising aflexible lamina including a metallic base member connected to andoperably supporting an overlay of asbestos material, said liner beingfashioned into four rectangular strips with each strip operable tooverlie one side of a rectangular duct, each of said liner strips havingembedded in the long edges thereof a flexible cable and extending withinsaid exhaust duct in the corners thereof to conform the rectangularliner strips to the interior surface of the exhaust duct.
 4. An exhaustduct system of the type utilized to vent grease laden vapors from acooking facility as defined in claim 3 and further comprising aplurality of pin locking assemblies pinning the liner to the interiorsurface of the exhaust duct, said pin locking assemblies eachcomprising, a base member fixedly attached to the interior surface ofthe exhaust duct, a post normally projecting inwardly within the exhaustduct from said base member and being operable to pass through the liner,and a locking pad having a central aperture operable to receive saidpost in interferring contact and to thereby retain the liner snugglyagainst the exhaust duct wall.
 5. A method for lining an exhaust duct ofthe type typically utilized to vent grease laden vapors from a cookingfacility comprising the steps of: a. providing a rectangular flexiblesheet of lining material; b. attaching flexible cables to the long edgesof said lining material; c. attaching a dual spool winch at the top ofthe exhaust duct; d. lowering a flexible cable from each winch spooldown through the exhaust conduit; e. attaching the free ends of thelowered flexible cables to the free ends of the cables attached to thelining material; f. turning the cables up on the dual spool winch toraise the liner material into the interior of the exhaust conduit; g.securing the lining material within the interior of the exhaust duct;and repeating steps (a)-(g) until the entire exhaust duct is lined withstrips of lining material.
 6. A method for maintaining an exhaust systemin a condition free from objectionable buildup of grease deposits asdefined in claim 5 wherein said step of lining the interior surface ofthe exhaust duct comprises: combining into a flexible lamina a metallicbase member and a layer of asbestos sheet material, and attaching theflexible lamina within and throughout the extent of the exhaust duct. 7.A method for maintaining an exhaust system in a condition free fromobjectionable buildup of grease deposits as defined in claim 6 whereinsaid step of combining further includes the step of: positioning a vaporbarrier between said metallic base member and said sheet of asbestosprior to attaching the flexible lamina within the interior of theexhaust duct.
 8. A method for lining an exhaust duct of the typetypically utilized to vent grease laden vapors from a cooking facilityas defined in claim 5 wherein said step of providing a flexible linercomprises the step of: laminating a rectangular strip of metallic basemember and a coextensive rectangular strIp of asbestos sheet material.9. A method for lining an exhaust duct of the type typically utilized tovent grease laden vapors from a cooking facility as defined in claim 8wherein said step of laminating further includes: positioning arectangular vapor barrier strip between the metallic base member and theasbestos sheet material.